The present invention is directed to locking hydraulic actuators and a method for locking a hydraulic actuator in a predetermined position.
Locking hydraulic actuators are commonly used in situations where it is desirable to have a hydraulic actuator which can be secured in a predetermined position without the necessity of maintaining the presence of hydraulic supply pressure. Locking hydraulic actuators are commonly used, for example, in the aircraft industry for lowering or raising landing gear. All prior art locking actuators utilize some sort of internal mechanical locking means. For example, most modern prior art locking actuators utilize a plurality of radially moving locking members which engage into a groove to lock the hydraulic actuator in a predetermined position. These generally contain a shear element physically wedged between the stationary actuator cylinder and the moving piston. Dynamic loads reacted to by relatively small metal to metal contact areas induce large stress concentrations within the locking members and are thus subject to premature wear.
Accordingly, there is a need for a locking hydraulic actuator that is structurally simple, easy and inexpensive to manufacture, durable, and which distribute the locking load both uniformly and symmetrically.